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Hydraulic Roll Changers in Rolling Mill Applications


Hydraulic cylinders are used to power working roll changing systems in cold or hot rolling mill applications. Typically, changing a working roll can take nearly an hour. With automatic working roll changers, the old roll can be interchanged with a new roll in a few minutes.

Automatic Working Roll Changers

Hydraulic working roll changers consist of a hydraulic power system that drives the piston rods of hydraulic cylinders mounted in a mill stand. Working rolls are usually supported by neck bearings, and fitted into roll chocks that can move up or down in the mill housing. Hydraulic rams or cylinders are mounted between the upper and lower working rolls or beneath the backup rolls. When actuated, the hydraulic rams apply an upward force to the upper and lower roll chocks so they can be lifted or lowered from their housing. In another type of mill design, the hydraulic rams are mounted on a hinged plate that is raised or lowered by the cylinders to push the old roll out of the mill. As the working roll is lifted out of its chocks, the old roll is hooked onto an overhead crane and finally removed from the mill stand. A new working roll is inserted, via an overhead crane, into the mill housing and lowered into the chocks by the hydraulic ram. Back up rolls can also be changed out using a similar type of hydraulic system, with the hydraulic cylinders installed below the bottom of backup roll chocks. The typical hydraulic pressure to power the roll changing cylinders is about 1400 to 2100 psi. The traditional method of transporting the old rolls is by overhead crane and a changing unit that is attached to the roll neck. But today, the newer mills are designed with automatic roll changers that use a carriage assembly to accept the rolls that are withdrawn from the mill housing while positioning new working rolls into the mill.

Hydraulic Roll Changer Vehicles

Once the working rolls are removed from the mill stand, they needed to be transported within the milling plant’s facilities from operations area to the dock for shipping. This is usually accomplished with an overhead crane. However, there are roll changer vehicles that can replace the use of overhead cranes for moving old rolls throughout the plant. These mobile vehicles are hydraulically powered and typically rated for maximum capacities in the range of 120 tons. The vehicles are multi-axle and designed in such a way that will spread the load over a wide surface area in order to distribute the load. The vehicle is computer controlled and is capable of quick changeouts of working rolls. The vehicle has an extracting mechanism that can align the vehicle to accept the old roll and insert a new roll in the mill. The primary benefit of a roll changing vehicle is to improve mill efficiencies by not requiring the use of an overhead crane. These portable transport vehicles also eliminate the need for rail systems that typically convey the old rolls in the mill facilities.